An enhanced uplink mechanism has been introduced for the Third Generation Partnership Project (3GPP) standards. As a part of the enhanced uplink mechanism and improved Layer 2 (L2), new functional entities have been introduced in the medium access control (MAC) including enhanced MAC-e/es entities. In a wireless transmit/receive unit (WTRU), the enhanced MAC-e/es are considered one single sublayer. However in the network side the enhanced MAC-e and the enhanced MAC-es entities may be considered separate, with the enhanced MAC-e residing in the Node-B and the enhanced MAC-es residing in the serving radio network controller (SRNC). One enhanced MAC-e and one enhanced MAC-es entity are present for each WTRU in the Node B and in the SRNC, respectively. The entities are separate in the network so that the more real-time critical functionality of enhanced MAC-e may be placed into the Node-B.
FIG. 1 is a block diagram of an enhanced MAC entity 100 of a WTRU. The enhanced MAC in the WTRU comprises a hybrid automatic repeat-request (HARQ) module, a multiplexing and transmission sequence number (TSN) setting module, an enhanced uplink transport format combination (E-TFC) selection module, and two segmentation modules.
The HARQ module performs the MAC functions relating to the HARQ protocol, including storing enhanced MAC-e payloads and re-transmitting them. The HARQ module determines the E-TFC, the retransmission sequence number (RSN), and the power offset to be used by Layer 1 (L1).
The multiplexing and TSN module concatenates multiple MAC-d protocol data units (PDUs) into enhanced MAC-es PDUs, and multiplexes one or multiple enhanced MAC-es PDUs into a single enhanced MAC-e PDU, to be transmitted in a subsequent transmission time interval (TTI), as instructed by the E-TFC selection module.
The E-TFC selection module performs E-TFC selection according to scheduling information, relative and absolute grants received from a UMTS Terrestrial Radio Access Network (UTRAN) via L1 signalling, and a serving grant signalled through the RRC for arbitration among the different flows mapped on the E-DCH.
The segmentation module performs segmenting of the MAC-d PDUs.
FIGS. 2 and 2A show the enhanced MAC-e and enhanced MAC-es entities located at the Node-B and RNCs, respectively. Referring to FIG. 2, the enhanced MAC-es sublayer manages E-DCH specific functionality. The enhanced MAC-es entity comprises a disassembly module, a reordering and queue distribution module, a reordering/combining module, and a reassembly module.
The reordering queue distribution module routes the enhanced MAC-es PDUs to the correct reordering buffer based on the serving radio network controller (SRNC) configuration and based on the logical channel identity.
The reordering/combining module reorders received enhanced MAC-es PDUs according to the received TSN and Node-B tagging, (i.e. CFN, subframe number). Enhanced MAC-es PDUs with consecutive TSNs are delivered to the disassembly module upon reception.
The macro diversity selection module operates in the enhanced MAC-es, in case of soft handover with multiple Node-Bs.
The disassembly module is responsible for disassembly of enhanced MAC-es PDUs, including removal of the enhanced MAC-es header.
The reassembly function reassembles segmented MAC-d PDUs, and delivers the MAC-d PDUs to the correct MAC-d entity.
Referring to FIG. 2A, shows a MAC-e entity in communication with an E-DCH scheduling module. The enhanced MAC-e entity comprises an E-DCH control module, a de-multiplexing module, and a HARQ entity.
The E-DCH scheduling module manages E-DCH cell resources between WTRUs. Based on scheduling requests, scheduling grants are determined and transmitted.
The E-DCH control module is responsible for reception of scheduling requests and transmission of scheduling grants.
The de-multiplexing module performs the de-multiplexing of enhanced MAC-e PDUs into enhanced MAC-es PDUs. Enhanced MAC-es PDUs are forwarded to the SRNC in their associated MAC-d flow.
The HARQ module may support multiple HARQ processes. Each process is responsible for generating ACKs or NACKs indicating delivery status of E-DCH transmissions.
FIG. 3 shows the radio resource controller (RRC) service states of a 3GPP WTRU with an enhanced uplink. The WTRU may operate in several states which depend on the user activity. The following states have been defined: Idle, Cell_DCH, Cell_FACH, URA_PCH and Cell_PCH. The RRC state changes are controlled by the network using RNC parameters, the WTRU does not decide to perform state changes by itself.
In the Cell_DCH state, a dedicated physical channel is allocated to the WTRU in the uplink and the downlink. The WTRU is known on a cell level according to its current active set. The WTRU may use dedicated transport channels, shared transport channels, or a combination of these transport channels.
A WTRU is in the Cell_FACH state if it has been assigned to use the common control channels (e.g. CPCH). In the Cell_FACH state, no dedicated physical channel is allocated to the WTRU, and the WTRU continuously monitors a FACH (e.g., S-CCPCH) or a High Speed Downlink Shared Channel (HS-DSCH) in the downlink. The WTRU is assigned a default common or shared transport channel in the uplink (e.g. RACH) that it can use anytime according to the access procedure for that transport channel. The position of the WTRU is known by the UTRAN on a cell level according to the cell where the WTRU last performed a cell update.
In the Cell_PCH state, no dedicated physical channel is allocated to the WTRU. The WTRU selects a PCH, and uses discontinuous reception for monitoring the selected PCH via an associated PICH. No uplink activity is possible. The position of the WTRU is known by the UTRAN on a cell level according to the cell where the WTRU last performed a cell update in the CELL_FACH state.
In the URA_PCH state, no dedicated channel is allocated to the WTRU. The WTRU selects a PCH, and uses discontinuous reception for monitoring the selected PCH via an associated PICH. No uplink activity is possible. The location of the WTRU is known on a UTRAN registration area level according to the URA assigned to the WTRU during the last URA update in the Cell_FACH state.
As a part of the enhanced uplink mechanism an, enhanced random access channel (E-RACH) has been introduced for the CELL_FACH state. The E-RACH refers to the use of the enhanced dedicated channel (E-DCH) in the Cell_FACH state or the resource/physical channel used by the WTRU for uplink contention-based access. Previously, the only uplink mechanism for a WTRU in the Cell_FACH state was transmission via the RACH using a slotted-Aloha approach with an acquisition indication message.
With the introduction of the E-DCH in the Cell_FACH state, the WTRUs and the network may require the introduction of enhanced MAC-e/es entities in order to enable the communication between the WTRU and the network. Due to the nature of the E-DCH operation in the Cell_FACH state, a number of issues may arise with the E-DCH MAC resources. One of the issues relates to defining how and when to set up the enhanced MAC-e/es entities. In addition, rules regarding the location of the enhanced MAC-e/es entities and whether the enhanced MAC-e and/or enhanced MAC-es are common or dedicated entities are desired. Also, additional RNC to Node-B interface (Tub) signaling for the setup and management of the MAC entities are desired. Accordingly methods to manage E-DCH resources and to manage TSN numbering are desired.